Improvement of foam lacing of beer.

Abstract
In previous studies, three of the authors of this paper made some important discoveries relating to beer foam quality, including the identification of foam positive proteins and the detection and explanation of the negative effects on foam quality of basic amino acids (arginine, lysine, histidine, etc.) and yeast protease. A method for measuring the adhesion of foam to the side of the glass as the beer is consumed (known as "foam cling" or "lacing") is described. A 633 ml beer sample (the volume of a common size of large beer bottle used in Japan) is poured into a 2 litre glass cylinder through a funnel and left to stand for 30 minutes, by which time the foam head has partially collapsed, leaving some lacing on the sides of the cylinder. The image of the cylinder, recorded on photosensitive paper, is used to calculate the area of the lacing. The average lacing area, in sq cm, of three identical samples constitutes the "SHV value" (stated to be derived from "Schaumhaftvermoegen", the German word for foam cling, although all the authors are Japanese). Beers with normal foam quality should have SHV values between 90 and 140 sq cm; a value below 90 indicates poor foam quality, while one above 140 is better than average. Experiments showing the effects of variations in the brewing process on factors influencing foam quality, as indicated by the SHV value, are described, including the foam negative effects of lower mashing in temperatures and mash pH (which can produce more amino acids in the wort than are required by the yeast, due to excessive proteolytic activity during mashing, so that residual amino acids persist in the beer) and of delaying the cropping of the yeast until after the green beer is cooled instead of cropping as soon as primary fermentation is complete (because the delay can lead to the death of yeast cells in the beer and the release of protease from the dead cells) as well as the positive effect of a 20 minute rest at 71 degrees C during mashing (which increases the foaming protein content of the wort and therefore of the beer).
Keywords : beer brewing foam foam stability measurement quality